PWM output on CNC BOB

[jolyonjenkins]

Hi

I have a cheap generic Chinese breakout board - like this https://www.ebay.co.uk/itm/333905827471
but it has no documentation and the listing is obscure.

It has a pin marked 0-10V PWM output, which is good - my CNC spindle controller board wants a variable DC voltage to control the spindle speed. However, I'm not at all clear how that variable voltage is produced. I'm using LinuxCNC, and the setting for the parallel port is that pin 16 is PWM output. I presume that LinuxCNC produces a high frequency square wave on pin 16, but I can't get my head round how the BOB knows that pin 16 is the one that controls the voltage on the PWM output. If if does ...

[Clive S]

Hi

I have a cheap generic Chinese breakout board - like this https://www.ebay.co.uk/itm/333905827471
but it has no documentation and the listing is obscure.

It has a pin marked 0-10V PWM output, which is good - my CNC spindle controller board wants a variable DC voltage to control the spindle speed. However, I'm not at all clear how that variable voltage is produced. I'm using LinuxCNC, and the setting for the parallel port is that pin 16 is PWM output. I presume that LinuxCNC produces a high frequency square wave on pin 16, but I can't get my head round how the BOB knows that pin 16 is the one that controls the voltage on the PWM output. If if does ...

For the bob you are using you will have to put 12-24V on the centre two terminals ( near the relay) in order to get the 0-10V out as well. It also need the 12-24v for the inputs to work

I know this is not the same bob but it might give you a clue


# SPINDLE S
#*******************

setp pid.s.Pgain [SPINDLE_9]P
setp pid.s.Igain [SPINDLE_9]I
setp pid.s.Dgain [SPINDLE_9]D
setp pid.s.bias [SPINDLE_9]BIAS
setp pid.s.FF0 [SPINDLE_9]FF0
setp pid.s.FF1 [SPINDLE_9]FF1
setp pid.s.FF2 [SPINDLE_9]FF2
setp pid.s.deadband [SPINDLE_9]DEADBAND
setp pid.s.maxoutput [SPINDLE_9]MAX_OUTPUT
setp pid.s.error-previous-target true

net spindle-index-enable <=> pid.s.index-enable
net spindle-enable => pid.s.enable
net spindle-vel-cmd-rpm => pid.s.command
net spindle-vel-fb-rpm => pid.s.feedback
net spindle-output <= pid.s.output

# ---setup spindle control signals---

net spindle-vel-cmd-rps <= motion.spindle-speed-out-rps
net spindle-vel-cmd-rps-abs <= motion.spindle-speed-out-rps-abs
#net spindle-vel-cmd-rpm <= motion.spindle-speed-out
#net spindle-vel-cmd-rpm-abs <= motion.spindle-speed-out-abs
net spindle-enable <= motion.spindle-on
net spindle-cw <= motion.spindle-forward
net spindle-ccw <= motion.spindle-reverse
net spindle-brake <= motion.spindle-brake
net spindle-revs => motion.spindle-revs
net spindle-at-speed => motion.spindle-at-speed
net spindle-vel-fb-rps => motion.spindle-speed-in
net spindle-index-enable <=> motion.spindle-index-enable

# ---Setup spindle at speed signals--- on bob relay pin DB 17

setp hm2_7i92.0.gpio.024.is_output 1

net spindle-enable hm2_7i92.0.gpio.024.out
sets spindle-at-speed true

#Below sets position of relay contacts on power up
setp hm2_7i92.0.gpio.024.invert_output true

#PWM Generator signal/setup

setp hm2_7i92.0.pwmgen.pwm_frequency 1500

setp hm2_7i92.0.pwmgen.00.output-type 1
setp hm2_7i92.0.pwmgen.00.scale 5000
setp hm2_7i92.0.pwmgen.00.enable true

net spindle-speed motion.spindle-speed-out-abs hm2_7i92.0.pwmgen.00.value

############

It might be easier to make another stepconf junk config then copy from that junk hal file the bits you need.

[jolyonjenkins]

Thanks.
But I don't think I've explained my confusion.
Assume the bob has the 12v in. There will be a variable DC voltage on the PWM pin. That voltage is controlled by the frequency of a signal on one of the pins, generated by linuxcnc. I can use stepconf to assign the pin that produces the signal. But how does the bob know which pin to expect the on?

[Clive S]

Thanks.
But I don't think I've explained my confusion.
Assume the bob has the 12v in. There will be a variable DC voltage on the PWM pin. That voltage is controlled by the frequency of a signal on one of the pins, generated by linuxcnc. I can use stepconf to assign the pin that produces the signal. But how does the bob know which pin to expect the on?

You have to tell Lcnc which pin to send it to.

Can you post the config

#### Spindle stuff ###

net spindle-cmd-rpm => pwmgen.0.value
net spindle-on <= spindle.0.on => pwmgen.0.enable
net spindle-pwm <= pwmgen.0.pwm
setp pwmgen.0.pwm-freq 100
setp pwmgen.0.scale 1000
setp pwmgen.0.offset 0.1

setp pwmgen.0.dither-pwm true

net spindle-cmd-rpm <= spindle.0.speed-out
net spindle-cmd-rpm-abs <= spindle.0.speed-out-abs
net spindle-cmd-rps <= spindle.0.speed-out-rps
net spindle-cmd-rps-abs <= spindle.0.speed-out-rps-abs
net spindle-at-speed => spindle.0.at-speed
net spindle-cw <= spindle.0.forward

### Parport Pins ###
setp parport.0.pin-01-out-invert 1
net spindle-pwm => parport.0.pin-01-out These are the pins on the bob
net spindle-cw => parport.0.pin-14-out
net spindle-on => parport.0.pin-17-out

[jolyonjenkins]

But how do I know which pin to send it to? I'm assuming that the bob is looking for a signal on a particular pin, which is determined by the hardware of the board. I don't have a problem with configuing Linuxcnc, but I don't see how I know which pin the board wants. I feel I am either missing some concept or being very stupid.

[jolyonjenkins]

But how do I know which pin to send it to? I'm assuming that the bob is looking for a signal on a particular pin, which is determined by the hardware of the board. I don't have a problem with configuing Linuxcnc, but I don't see how I know which pin the board wants. I feel I am either missing some concept or being very stupid.

[magicniner]

I feel I am either missing some concept or being very stupid.

You are in the process of learning why cheap hardware is cheap and that some of what you are paying for with better, more expensive products is adequate documentation and support ;-)

[Doddy]

The BoB has a hard-wired interface from one of the discrete outputs (I have a similar board, that's silk-screened "P1 - PWM" - so pin 1 is assigned by hardware design to the PWM circuit. No configuration, no nothing (you could hack the card, of course). There's nothing clever, just assign the same output in LinuxCNC to the hardwired assignment on the board.

Most BoBs are similar.

[jolyonjenkins]

The BoB has a hard-wired interface from one of the discrete outputs (I have a similar board, that's silk-screened "P1 - PWM" - so pin 1 is assigned by hardware design to the PWM circuit. No configuration, no nothing (you could hack the card, of course). There's nothing clever, just assign the same output in LinuxCNC to the hardwired assignment on the board.

Most BoBs are similar.

Thank you! That was the information I was after

[Paul H]

Hi
One thing to watch out for: check that your inverter to control the spindle is isolated from the mains that is to say the the 0 to 10v input is not at mains potential.. this should described in you manual for the inverter...
could be serious risk of electrical shock and the magic smoke will appear...

Best regards
Paul